1. Field
The present invention relates to a technique for processing photomask data and a photomask manufacturing technique using the same.
2. Description of Related Art
To produce the extremely fine patterns of today's large-scale integrated (LSI) semiconductor circuits, high precision patterning techniques are required. In high precision patterning, processing to correct pattern data, such as optical proximity correction, is applied to design data. Processing to correct pattern data is executed to form the pattern intended to be transferred over a semiconductor substrate from design data. In processing to correct pattern data, the pattern shape of design data is deformed by using a rulebase or optical simulation. For this reason, when processing to correct pattern data is to be applied, the volume of pattern data (which may as well be referred to as graphic symbols) becomes enormous along with the progress of the cutting-edge technology, and the processing time elongates. This invites a significantly extending trend of the mask data processing time taken to fabricate transfer masks for use in transfers.
In conventional processing to correct pattern data such as optical proximity correction, the pattern in the design data is corrected in accordance with a file of designated conditions (pattern interval, pattern width and optical conditions) on the basis of the relationship between the pattern data of the pattern to be worked on itself and adjoining pattern data. In such processing to correct pattern data, a higher processing speed is sought by using parallel correction processing and distributed processing on the design data. However, along with the increasing complexity of processing ensuing from the rising precision of correction processing, the growing fineness of the pattern invites an ever greater scale of pattern data. This invites a significant elongation of the execution time taken by the computer to accomplish correction processing.
The time taken by processing to correct pattern data tends to increase with the number of units of pattern data. Conventionally, correction is processed on all pattern data in accordance with a file of designated conditions (pattern interval, pattern width and optical conditions). However, as disclosed in National Publication of International Patent Application No. 2004-502961, it is also proposed to perform optical proximity correction while maintaining the hierarchical structure of design data.
Yet, when correction processing is to be executed by utilizing the hierarchical structure of design data, the regularity of the reiterative pattern is often disturbed by the influence of proximate patterns. As a consequence, the processing is not completed within the desired time limit, giving rise to a problem of an extended length of time taken by the processing. By another method to reduce the time taken by processing, as disclosed in Japanese Patent Laid-Open No. 2007-86587 and Japanese Patent Laid-Open No. 2005-84101, the pattern having gone through proximity correction may be directly registered into the design data as a library, and the library may be referenced as required. However, there is a problem as a matter of real execution that, unless the influences of patterns present around the library pattern are compensated for, no output of normal proximity correction processing can be obtained. Moreover, patterns around the library pattern differ with each individual semiconductor device to be designed. Even in the same semiconductor device, surrounding patterns differ with the position in which the library pattern is arranged. Therefore, this technique can provide no realistic solution.